1. Field of the Invention
The present invention relates to the gradual replacement of ozone-damaging Freon 12.RTM. refrigerant with a refrigerant that is less damaging to the ozone layer in systems designed to use Freon 12.RTM.. More particularly the present invention relates to an improved refrigerant composition, method and apparatus for refrigeration wherein two non-Freon 12 refrigerants are mixed in a defined ratio such that the temperature-pressure relationship of the mix approximates that of ozone-damaging Freon 12.RTM., especially at high operating temperatures. The mixture is compatible with Freon 12.RTM. so that it can be added to supplement and gradually replace ozone-damaging Freon 12.RTM.. A further particularity of the instant invention relates to an improved method and apparatus for refrigeration wherein refrigerant mixture is mixed with a soluble lubricating oil to provide lubrication to the apparatus. The lubricant is soluble in both the mixture of the invention and Freon 12.RTM. refrigerant.
2. General Background
Until recently, R-12 or dichlorodifluoromethane (hereinafter called "Freon 12.RTM."); While Freon 12.RTM. is a trade name of E. I. du Pont de Nemours & Co. Inc. for dicholordifluoromethane, hereinafter "Freon 12.RTM." is used in this specification to denote dicholorodifluoromethane, regardless of the source) was the major, if not sole refrigerant, used in automobile air-conditioners, refrigerators, freezers and window air-conditioning units.
Recently, however, Freon 12.RTM. has come under attack both nationally and internationally as an ozone layer-damaging chemical. In recent years, both the national and international scientific communities have linked Freon 12.RTM. with damage to the earth's protective ozone layer. Automobile air-conditioners, refrigerator/freezers and window air-conditioning units are believed to be a significant global source of ozone-damaging Freon 12.RTM..
In response to both scientific concern and a national and global outcry over the use of Freon 12.RTM. in air-conditioning, the United States Congress has acted to first reduce and then ban the use of Freon 12.RTM. in air-conditioning units.
One of the first areas in which the use of Freon 12.RTM. is to be phased out is in automobile air-conditioning. As a first step toward phasing out the use of Freon 12.RTM. in automobile air-conditioning units, Congress is phasing out the use of Freon 12.RTM. in new automobiles and has banned the sale of Freon 12.RTM. in small retail quantities for the do-it-yourself air-conditioner recharger market.
However, at the time of this application, the vast majority of automobiles in use in the United States contain Freon 12.RTM.-based air-conditioning units, and approximately 40% of new automobiles continue to contain Freon 12.RTM.-based air conditioners.
Prior to banning the retail sale of small quantities of Freon 12.RTM., owners of automobiles with Freon 12.RTM.-based air-conditioning units were able to recharge, or "top-off" the level of coolant in their automobile air-conditioners without the need for expensive professional service. Millions of units of Freon 12.RTM. recharging units were sold in the United States prior to being banned in January, 1994.
These Freon 12.RTM. recharger kits typically consisted of a 12 ounce aerosol can containing Freon 12.RTM.. The cans were fitted with an aerosol dispensing outlet that was compatible with a commercially available refrigeration manifold. In order to recharge an air-conditioning system, a customer needed to only fit the can to the manifold and discharge, or "drop in" the can's refrigerant charge directly into the air conditioning system, thus eliminating the need to bleed the system of existing Freon 12.RTM. before recharging.
Following Congress's ban on the retail sale of Freon 12.RTM. recharger kits, millions of automobile owners with Freon 12.RTM.-based air-conditioning units were left with no choice other than to seek expensive professional service to recharge their automotive air-conditioning units.
Also in response to Congress's ban on the use of Freon 12.RTM. in automobile air-conditioning, professional automotive service dealers began to retrofit existing Freon 12.RTM.-based air-conditioning units into new, non-freon 12 refrigerant-compatible units.
The refrigerant authorized by the Environmental Protection Agency (EPA) to replace Freon 12.RTM. in automobile air conditioners is tetrafluoroethane (hereinafter referred to as "134a"). Unfortunately, 134a has a markedly different temperature-pressure relationship at high operating temperatures than does Freon 12.RTM..
Because of this difference in the temperature-pressure relationship of Freon 12.RTM. and replacement 134a, existing Freon 12.RTM.-based systems cannot simply be bled of Freon 12.RTM. and refilled with 134a. Were Freon 12.RTM. to be replaced by 134a in a non-retrofitted Freon 12.RTM.-based air-conditioning unit, the unit could not be operated at high temperatures because the significantly higher pressure of 134a over Freon 12.RTM. would damage the unit. Hence, non-retrofitted, Freon 12.RTM.-based units that are simply refilled with replacement 134a are inoperative at high operating temperatures; thus, inoperative at precisely the time that air-conditioning is most desired.
Further, simply mixing 134a with existing Freon 12.RTM. in order to replenish, or "top off" the level of coolant is not feasible. When 134a is mixed with Freon 12.RTM., the mixture takes on the pressure characteristics of a higher pressure azeotrope, as opposed to Freon 12.RTM.. The temperature-pressure profile of 134a becomes markedly different from that of Freon 12.RTM. at temperatures within the high end of the normal refrigerant operating temperature range. Hence, replenishing lost Freon 12.RTM. with 134a in a Freon 12.RTM.-based air-conditioning system would lead to the same problems as the use of pure 134a in a non-retrofitted Freon 12.RTM.-based system: Damage to the system caused by 134a's high pressure at high operating temperatures.
In addition, 134a is insoluble with the lubricant used in existing, non-retrofit Freon 12.RTM.-based systems. Thus, mixing 134a with Freon 12.RTM. in a non-retrofit Freon 12.RTM.-based unit leads to loss of lubrication and subsequent damage to the system.
Hence, in the absence of Freon 12.RTM. recharger kits, owners of automobiles with Freon 12.RTM.-based air conditioners face but one choice when the level of their air-conditioning coolant was low: Professional service to--at a significant cost--to remove the existing Freon 12.RTM., and retrofit the system to be compatible with 134a gas.
Prior to January, 1994, owners of the millions of automobiles with Freon 12.RTM.-based air-conditioning units had a choice of whether to merely top off the level of air-conditioning coolant with an inexpensive do-it-yourself Freon 12.RTM. recharger kit or to undergo an expensive retro-fitting process. However, at the time of this application, owners of automobiles with Freon 12.RTM.-based air-conditioners no longer have this choice. They must undergo expensive professional maintenance, or discontinue the use and enjoyment their automobile air-conditioners.